Hydrogen is widely used in various industrial fields such as petroleum refining and chemical industry. Especially, hydrogen has recently attracted attention as a future energy medium, and studies on hydrogen have been conducted with a focus on the field of fuel cells. However, it becomes a great barrier against spread of the hydrogen energy that transportation and storage of hydrogen are difficult (see Non Patent Literature 1 below).
Hydrogen gas is a voluminous fuel having a large volume per unit of heat amount, and combustion heat of the hydrogen gas at 1 atm (0.1 MPa) is only 1/3000 of that of gasoline having the same volume. Therefore, there are conducted transportation and storage of hydrogen whose energy density is increased by means of compression at an extremely high pressure such as about 35 MPa or 70 MPa. However, there is a problem that the cost of a device required for compression of hydrogen such as a compressor for hydrogen or a high-pressure container for compressed hydrogen is high. Moreover, it is expected that development of infrastructure for supplying hydrogen whereby safety of the compressed hydrogen can be ensured needs enormous cost.
Also, a technique concerning transportation and storage of liquefied hydrogen has attracted attention. However, it is necessary for liquefaction of hydrogen to cool hydrogen to a very low temperature such as about −253° C. Therefore, an extremely high-performance and expensive insulating container is required for transportation and storage of liquefied hydrogen. Furthermore, since energy required for the liquefaction of hydrogen is high, there is a problem of a decrease in energy efficiency associated with the liquefaction of hydrogen.
In order to overcome the aforementioned problem concerning transportation and storage of hydrogen, various hydrogen storage materials such as hydrogen storage alloys have been developed and studied; however, a material having a satisfactory performance has not been found yet.
As a medium used for transportation and storage of hydrogen, an organic compound which forms an unsaturated bond by a dehydrogenation reaction and at the same time releases hydrogen has attracted attention. A representative example thereof includes organic hydrides such as methylcyclohexane. When the organic hydrides are used as the medium, it is possible to store hydrogen in the organic hydrides which are liquid at room temperature, and therefore, it is expected that the cost of constructing infrastructure for transportation and storage can be reduced (see Non Patent Literature 2 below). It is noted that a dehydrogenation catalyst is generally used in the dehydrogenation reaction of the organic compound. In order to prevent a reduction in activity of the dehydrogenation catalyst, especially a reduction in activity due to carbon precipitation, it is effective to add 5 to 20 mole % of hydrogen to the organic compound before the dehydrogenation reaction (see Non Patent Literature 3 below).
In Non Patent Literature 4 below, it is proposed that generation and purification of hydrogen are conducted effectively by combining a technique concerning the dehydrogenation reaction of methylcyclohexane, or the like with a hydrogen separation membrane in which a palladium layer is formed on a porous support.